<!DOCTYPE html>
<html>
  <head>
    <title>Select Element Demo</title>
    <style>
      .show-me {
        display: none;
      }
      
      select[value="yes"] + .show-me {
        display: block;
      }
    </style>
  </head>
  <body>
    <label for="select-demo">Do you want to show the input element?</label>
    <select id="select-demo" name="show">
      <option value="no">No</option>
      <option value="yes">Yes</option>
    </select>
    <input type="text" class="show-me" placeholder="Type something here...">
  </body>
</html>

